qt50 malossi jetting

matt boda1nz /

hey guys, looking for a little guidance on jetting.

1980 yamaha qt50

mikuni vm12 stock carb

k and n 2540 air filter (heavily oiled because i don't have a jet higher than 95 yet, got a 100 and 105 coming)

boyesen reeds

holeshot springs

mlm pipe

currently i'm running a 87.5 jet (again, k and n is heavily oiled)

needle is in the second position from the top (leaner side)

40 pilot jet.

so, here is my issue..

if i get going and top it out at 47 mph, then back off and drop down to mid throtte, sometimes i will have a knocking sound (it's not four strokeing, it's a metalic sound, i have read maybe this is pipe bang.. if i richen it up with the choke, or let the throttle all the way closed, it wont do this...... must be a lean midrange.

when i richen up the needle though, it richens the main at wot so much that it's a dog to get going.. like the needle is lifting out of the main jet so much it changes the main jet size...

would lowering my main and richening the needle fix this and cure my mid? just thinking while i am at work.

my pilot is a 40 and it is rich on the idle side.. i ordered a 30, 32.5, 35, 37.5 pilot.. i know i will have to play the tunning game.. but just want some thoughts

i am super happy with it so far, just want to cure my mid range, seems to be lean when i back off from wot.

plug is not being hit.

Re: qt50 malossi jetting

I would think that a bigger main would be the way to go the YT60 has a stock main jet of 92.5 and has the same carb and intake. Im thinking of starting with a 95 main with the same set up. lol same year too. I am kinda looking at it like is a bored out yt60 with a pipe.

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